The present invention is directed to an implantable cardiac patient monitor. The present invention is more particularly directed to an implantable cardiac patient monitor which, in addition to monitoring for various arrhythmias and ischemia of the heart, is also capable of monitoring heart rate variability of the heart.
Changes in beat-to-beat variability of the heart as an indicator of cardiac autonomic status, has been shown in the literature to be a predictor of long-term survival after acute myocardial infarction. Changes in beat-to-beat variability of the heart has also been shown to be a predictor of heart transplantation rejection.
More specifically, it has been shown in the literature that lower heart rate variability in patients who have had a recent myocardial infarction may be more vulnerable to sudden cardiac death (SCD). However, many patients who have progressive coronary artery disease may also have asymptomatic (silent) myocardial infarctions. If undetected, the risk of a sudden cardiac death episode in these patients may increase. The only way to discern a change in this risk factor is through a cardiac monitor capable of continuously monitoring heart rate variability which would provide this necessary feedback. Unfortunately, the prior art has not provided such a continuously monitoring system.
Patients who have undergone a heart transplant are presently monitored for transplant rejection by endocardial biopsy at regular prescribed time intervals. Endocardial biopsies are both costly and can only provide clinical feedback at the prescribed intervals. The hearts of patients with transplanted hearts have low heart rate variability due to the lack of neural connections. The literature has shown that an increase in heart rate variability within these patients also provides an indication of transplant rejection. Hence, there is a need in the art for a cardiac monitor capable of providing continuous monitoring of the heart rate variability of these patients. Such a cardiac monitor could reduce the number and frequency of such expensive, invasive procedures. In addition, with such a cardiac monitor, a rejection episode may be detected earlier than heretofore possible thus providing more immediate treatment to the patient suffering from heart transplantation rejection.